1. Field of the Invention
The present invention relates to a light emitting diode, and more particularly, to a light emitting diode, wherein a lens can be easily formed thereon and an attachment force of the lens thereto is improved.
2. Discussion of the Background
A light emitting diode (LED) is a device which emits light due to recombination of electrons and holes in a p-n junction structure of a semiconductor. The LED has features such as low power consumption, long life span, narrow installation space and high resistance to vibration. Accordingly, the LED has been used in various fields and its applications are expanded to parts for a variety of information processing and communication equipment. As the applications of the LED are expanded, the LEDs having high luminance and color rendering index are further required. Thus, studies have been continuously conducted on a lens for focusing light, a chip, and materials suitable for fabricating the LED.
Meanwhile, conventional LEDs are provided in various types such as a lamp type LED and a chip type LED. In addition, there is provided an LED that has improved luminance by forming a reflector surrounding a light emitting chip.
FIGS. 1 and 2 are sectional views illustrating examples of such a conventional LED.
Referring to these figures, the conventional LED includes a substrate 1, electrodes 2 and 3 formed on the substrate 1, a light emitting chip 5 mounted on the electrode 2, and a reflector 4 formed on the substrate 1 and having a hollow portion to surround the light emitting chip 5.
The LED has a lens unit at its upper portion to improve light emission efficiency by controlling a refraction of light. To this end, as shown in FIG. 1, the LED includes a molding portion 7 formed in the hollow portion of the reflector 4 to encapsulate the light emitting chip 5, and a lens 8 separately manufactured and attached to upper ends of the reflector 4 and the molding portion 7.
Korean Patent Laid-Open Publication No. 2005-0012372 discloses an LED package having high luminance and superior heat dissipation by mounting a plurality of high-power LED chips in a package type. The LED package includes a wiring portion, the plurality of LED chips, a reflection cup portion, and a lens portion disposed on the reflection cup portion to transmit light emitted from the LED chips outwardly. The lens portion is coupled to the reflection cup portion by means of an adhesive with high heat resistance. Furthermore, pins, which are used for mounting the LED package, may be arranged along an edge of the lens portion after coupling the lens with the reflection cup portion. The pins strongly fix the lens to the LED package. However, this LED with such a structure has disadvantages in that the lens may be easily separated from the LED package when the adhesive is not cured completely, and that reliability may be lowered due to deformation of the adhesive. Further, since the processes for fixing the lens portion using the adhesive or pins are added, the overall fabricating processes are complicated. In addition, since it is difficult to precisely align the lens in place, an error in the position of the lens may occur, resulting in degradation of light emission efficiency.
Alternatively, as shown in FIG. 2, a lens-shaped molding portion 9 may be formed inside the reflector 4. The constitution and effects of this LED are specifically disclosed in Korean Patent Laid-Open Publication No. 2005-0082711. However, the technique of forming the lens-shaped molding portion 9 increases fabrication cost and is not suitable for mass production. This technique has a limitation on improvement of efficiency as compared with the case where the lens is separately manufactured and then attached.